The present invention is related to Japanese patent application No. 2000-225501, filed Jul. 26, 2000; the contents of which are incorporated herein by reference.
The present invention relates to an integrated vehicle control system for integratedly controlling multiple components mounted on a vehicle, and more particularly, the present invention relates to an integrated vehicle control system that provides a quick exchange of important information between such components.
Recently, to cope with an increase in system scale due to an increase in the number of components of a vehicle, there has been proposed an integrated vehicle control system which permits exchange of data between control elements provided for each of plural such vehicular components and which thereby realizes stable control for the vehicle as a whole.
For example, in an integrated vehicle control system disclosed in JP-A No. Hei 10-250417, control elements for controlling engine output, driving force and braking force and control elements for controlling vehicular operation characteristics are arranged in the form of a hierarchical structure. And, there is provided an entire vehicle adjusting unit which controls those control elements integratedly. According to the integrated vehicle control system, by supply required characteristics successively from high to low hierarchical level, component operation (actuator) is determined where each control element controls, and an optimum control is realized with the entire vehicle.
Thus, by dividing the vehicular control system into multiple systems, the number of components of a control system that is subject to design modification to match a change in system specification is decreased and the period required for the design modification is shortened thereby. Or, by keeping the components independent of each other, it is possible to develop components concurrently and shorten the development period for a vehicle as a whole.
However, in such a system wherein the vehicle is controlled in a hierarchical manner, even when urgent information is output from a certain control element to another control element, control is performed through the foregoing entire vehicle adjusting unit, resulting in a response delay. Accordingly, there is a fear that the vehicle behavior may become unstable.
For example, a problem arises in case of making an ACC (Adaptive Cruise Control) wherein a vehicle-to-vehicle distance between this vehicle and another vehicle traveling ahead is measured and the driving and braking force of this vehicle are controlled according to the thus-measured vehicle-to-vehicle distance, thereby maintaining an appropriate vehicle-to-vehicle distance. More particularly, when the vehicle traveling ahead decelerates suddenly or when a vehicle breaks into the front of this vehicle at a very short distance, the control decelerates the vehicle rapidly for preventing a rear-end collision. When this control is made by the engine control for example, the throttle valve is fully closed to diminish the driving force if the engine is in operation. If the control for deceleration is made by a transmission control, the gear shift range (change gear ratio) is switched to a low speed. Further, if brake control is used, brakes are applied.
However, arithmetic operations for the above controls are generally performed according to a predetermined cycle, so the actuator operation delays corresponding to the arithmetic operation cycle. In many cases, this arithmetic operation cycle is set longer than an operation limit of each actuator, i.e., longer than a cycle below which it is impossible to make a response even if the actuator is driven. In this case, therefore, a delay in operation of the actuator is so slight as causes no problem in normal vehicular operations, but causes a problem in case of an urgent operation.
Particularly, where a portion (the entire vehicle adjusting unit in the above example) which determined a behavior of the entire vehicle and a portion which drives actuators are provided on separate units and are connected together through a communication line, a response delay caused by communication is added and the danger of collision increases.
A problem arises also where on a road surface having a small coefficient of friction, such as a frozen road, the system must exhibit a traction function to prevent wheel spin and allow the vehicle to travel stably by adjusting both braking force and generated torque from the engine. For example, if the brake system becomes deteriorated, it is necessary that generated torque be adjusted by only the engine to allow the vehicle to travel stably. But, it is necessary to quickly execute an engine control processing for the deteriorated function of the brakes.
Particularly, in the foregoing unexamined publication, information of this deterioration (urgent information) is transmitted while going back the hierarchy to a level at which a command can be issued from the brake side to the engine side, and a command is issued to the engine on the basis thereof. In this case, if the engine and the brakes, as well as a portion which outputs operation guides to the engine and the brakes, are provided on separate units connected through a communication line, the above urgent information passes the communication line many times and the influence of the resulting delay in response is by no means negligible for maintaining the vehicle stable.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are intended for purposes of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. In the drawings:
The present invention has been accomplished in view of the above-mentioned drawbacks and it is an object of the invention to provide a system for integratedly controlling plural components mounted on a vehicle and capable of effecting a quick exchange of important information between components and keeping the vehicle behavior stable.
For achieving the above-mentioned object, in a first aspect of the present invention, there is provided an integrated vehicle control system wherein plural components mounted on a vehicle are respectively controlled by plural component control units corresponding to those components. A manager control unit of a higher order than the component control units issues an operation guide command for controlling the components. The manager control unit and the component control units, as well as the component control units themselves, are respectively connected through communication lines.
Therefore, the behaviors of the components are controlled respectively by the corresponding component control units and the behavior of the entire vehicle to be controlled can be controlled by the manager control unit. Thus, also in the system of the present invention, as is the case with the foregoing conventional system, when part of the components is changed due to a change in specification for example, all that is required is merely altering the corresponding component control unit. In system design, moreover, it suffices to design each control unit individually and therefore it is possible to shorten the development period.
In each component control unit, a manipulated variable (controlled variable) calculating means calculates a manipulated variable of the corresponding component according to an operation guide received from the manager control unit and a control means controls the component based on the manipulated variable thus calculated. Further, an important information transmitting means is provided in at least one of the plural component control units.
Based on an operational condition of the component concerned, the important information transmitting means determines whether an urgent control for another component control unit is necessary or not. If the result is affirmative, the means transmits important information for the urgent control directly to another component control unit through the communication line. Then, the control means in the component control unit which has received the important information, controls the component according to the important information.
The xe2x80x9cimportant informationxe2x80x9d as referred to herein indicates control information of a high urgency to be used for the operation of each component for avoiding, for example, collision of the vehicle, occurrence of an abnormal shock against the vehicle body, or the destruction of vehicular constituent parts. It is different from control information (general information) for other processings, i.e., control information to be used for the operation of each component in normal vehicular traveling.
Thus, according to this integrated vehicle control system, if the operational condition of each component is one in normal control, the important information transmitting means determines this information to be general information and does not function at all. As in the foregoing conventional system, this general information is once transmitted to the manager control unit, which in turn determines an operation guide for each component taking the general information, as well as other information pieces, into account. The operation guides thus determined are transmitted to the corresponding component control units.
On the other hand, in the event there occurs urgent information in a component, the important information transmitting means determines the information that is important information and transmits this important information to the control means in the corresponding component control unit directly without going through the manager control unit.
Therefore, the control means in the component control unit which has received the important information can control the corresponding component immediately according to the important information. As a result, the delay in response which occurred in the conventional system due to going through the manager control unit no longer occurs. And, it is possible to quickly cope with a vehicular urgent condition and keep the vehicular behavior stable.
Although a description has been given about the configuration where if important information occurs in a certain component control unit, a quick exchange of important information can be done between the component control unit and another component control unit, there is a case where important information occurs in the manager control unit and it is necessary to perform a quick processing based on the important information. A configuration meeting such a demand is adopted by an integrated vehicle control system according to the second aspect of the present invention.
In the second aspect of the invention, an entire vehicular operation determining means in a manager control unit determines an operation guide for the entire vehicle based on operation information on components received from component control units through a communication line, then based on the operation guide for the entire vehicle an operation guide determining means determines an operation guide for each component.
If each operation guide determined by the operation guide determining means is general information indicative of normal control, a general information transmitting means transmits this general information to the corresponding component control unit through the operation guide determining means. But if the operation guide for the entire vehicle determined by the entire vehicle operation determining means is important information, a second important information transmitting means transmits this important information to the corresponding component control unit directly without going through the operation guide determining means.
Thus, since the operation guide determining unit is not gone through, the second important information transmitting means can transmit important information to the corresponding component control unit side quickly. The control means in the component control unit which has received the important information, controls the corresponding component immediately according to the important information. Thus, also upon occurrence of urgent information in the manager control unit, it is possible to take a quick countermeasure and keep the vehicle behavior stable.
As to the exchange of important information between component control units in the above configuration, there may be adopted a mode wherein when important information occurs in one component control unit and is to be transmitted to another component control unit, the one component control unit transmits the contents of the important information or an operation guide based thereon to another component control unit. Then, a manipulated variable calculating means in the another component control unit which has received it calculates a predetermined control variable based on the operation guide, and the control means concerned executes a control based on the operation guide. Also as to the exchange of important information between the manager control unit and component control units, there may be adopted a configuration wherein the manager control unit transmits only an operation guide for a component control unit as important information to the component control unit. And, a predetermined manipulated variable is calculated on the component control unit side which has received it. This mode is preferred from the standpoint of maintaining the independence of the manager control unit and component control units and shortening each development period.
However, in such a configuration wherein only an operation guide is transmitted from the manager control unit or from one component control unit to a corresponding component control unit, a manipulated variable intended by the manager control unit or one component control unit is not always set on the corresponding component control unit side in the case of an operation control which must be done urgently. For example, where the corresponding component control unit is an engine control unit, even if an operation guide for a certain reduction of torque is output from the manager control unit or one component control unit, various control variables, including throttle opening and fuel injection volume, are combined to realize the decrease of torque in the engine control unit. In this case, even if the manager control unit or one component control unit side intends to only control in a fully closed state of the throttle valve, such a control is not always executed on the engine control unit side.
Therefore, a mode may be adopted wherein a manipulated variable is calculated on the manager control unit side or on one component control unit side.
As to the exchange of important information between component control units, there may be adopted a configuration according to the third aspect of the present invention. Here, if it turns out from the operational condition of one component that an urgent control is needed for another specific component, a second manipulated variable calculating means in the one component control unit calculates a manipulated variable for controlling the specific component and the important information transmitting means transmits the thus-calculated manipulated variable as important information to the control means in the component control unit which controls the specific component. In this case, the control means in the component control unit which received the important information controls the specific component according to the received manipulated variable.
As to the exchange of important information between the manager control unit and the component control units, there may be adopted a configuration according to the fourth aspect of the present invention wherein the manager control unit is provided with a manipulated variable calculating means. Here, when the operation guide for the entire vehicle determined by the entire vehicle operation determining means is important information, the manipulated variable calculating means calculates a manipulated variable for controlling a specific component according to the important information. The second important information transmitting means transmits the thus-calculated manipulated variable as important information directly to the control means in the component control unit which controls the specific component. In this case, upon receipt of the manipulated variable transmitted as important information from the second important information transmitting means, the control means in the component control unit controls the component according to the received manipulated variable.
With such a configuration, the component corresponding to the specific component control unit can be controlled based on the manipulated variable intended by the manager control unit or one component control unit. Moreover, since such a calculated manipulated variable is transmitted directly to the control means without going through the manipulated variable calculating means, the processing in the specific component control unit can be done quickly.
In the manager control unit and the component control units, there may simultaneously occur multiple types of information portions as important information portions. In this case, there may be adopted a configuration according to the fifth aspect of the present invention wherein the important information transmitting means and the second important information transmitting means transmit those important information potions according to a predetermined priority sequence.
Likewise, the component control units may receive plural types of information portions simultaneously as important information portions. In this case there may be adopted a configuration according to the sixth aspect of the present invention wherein the control means in the component control units executes control processing based on those important information portions according to a predetermined priority sequence.
Where the manipulated variable calculating means in the manager control unit takes the mode of calculating a manipulated variable according to only an operation guide based on important information and if the operation guide based on that important information and the operation guide which the operation guide determining means decided just before are greatly different from each other, vehicle may be shocked due to an abrupt change in control based on those operation guides. To avoid such an inconvenience, there may be adopted a configuration according to a seventh aspect of the present invention wherein the manipulated variable calculating means, when calculating a manipulated variable based on important information, makes reference to the operation guide decided just before by the operation guide determining means. By so doing, when it is determined that a sudden change in control will occur due to a change of operation guide, there may be adopted such a control form as approaches the control processing based on important information according to the degree of urgency indicated by the important information. More specifically, if the degree of urgency is not so high, there may be performed a processing such as a gentle shift of the control, whereby the vehicle behavior can be maintained more stably.
As concrete examples of the exchange of important information referred to above, there are considered various examples. For example, according to the eighth aspect of the present invention there is provided an integrated vehicle control system having, as the component control units, a power control unit for controlling a driving force generator mounted as a component on the vehicle and a brake control unit for controlling brakes mounted as a component on the vehicle, wherein when the function of the brakes is deteriorated, the brake control unit transmits to the power control unit a command to the effect of decreasing the driving force of the driving force generator as important information.
With such a configuration, it is possible to assist the brake control for the deteriorated brakes and thereby possible to prevent the occurrence of an accident such as collision of the vehicle with an object present ahead of the vehicle.
In the ninth aspect of the present invention, there is provided an integrated vehicle control system having, as the component control units, a power control unit for controlling a driving force generator mounted on the vehicle and a transmission control unit for controlling a transmission mounted on the vehicle. Wherein, during a shifting operation of the transmission, the transmission control unit transmits to the power control unit a command to the effect of decreasing the driving force of the driving force generator as important information.
According to this configuration it is possible to suppress shock which the vehicle receives during shifting. As the driving force generator which the power control unit controls, there is mentioned one which is driven by power control such as a motor drive. But when adopting an internal combustion engine as in the tenth aspect of the present invention, there is considered, as the control means in the power control unit, one which executes, when decreasing the driving force of the engine according to important information, at least one of such known controls as an intake volume decreasing control for decreasing the amount of intake air to the engine, an ignition timing retarding control for retarding the ignition timing for the engine, and an injection volume decreasing control for decreasing the amount of fuel to be injected to the engine. With the injection volume decreasing control is included a control of making the injection volume zero, i.e., an injection cut-off control.
A transmission equipped with a torque converter may be provided with a lock-up mechanism for the improvement of fuel economy. In such a transmission, input and output of the torque converter are directly coupled together mechanically by a lock-up clutch in a relatively high vehicle speed region, whereby a transfer loss caused by slippage in the torque converter is eliminated and fuel economy is improved.
In a lock-up condition, however, vibrations and changes in torque which have been absorbed are no longer absorbed due to slippage in the torque converter, so that, for example, when the engine torque changes suddenly, it is transmitted as a shock to the vehicle driver. Such an inconvenience can be avoided by adopting a configuration according the eleventh aspect of the present invention wherein when suddenly changing the air-fuel ratio during combustion of the engine, the power control unit transmits a command to release the lock-up mechanism of the transmission as important information to the transmission control unit.
By thus releasing the lock-up mechanism during sudden change in engine torque, the sudden change in engine torque is transmitted to the transmission in a mitigated state by the torque converter, so that the shock generated in the vehicle can be suppressed.
During lock-up, there also is a problem that the likelihood of engine stall on sudden braking increases, other than the transfer of vibrations and changes of torque. For example, if a sudden brake is applied when the vehicle is traveling on a road having a small coefficient of friction such as a snow-covered road or a frozen road, the wheels may be locked, that is, the number of revolutions of driving wheels may become zero. As such, if the torque converter is in a lock-up condition, the engine and the wheels assume a mechanically connected state, so that the rotation of the engine is stopped, causing engine stall. Even if the vehicle has an anti-lock function to decrease the braking force of the brakes to prevent locking of the wheels upon occurrence of wheel locking, it is impossible to avoid engine stall completely.
For avoiding such an inconvenience, there may be adopted a configuration according to the twelfth aspect of the present invention wherein at the time of starting the operation of the brakes, the brake control unit transmits to the transmission control unit a command to the effect of releasing the lock-up mechanism in the transmission as important information.
According to this configuration, lock-up is cancelled when the brakes are in operation, so even upon locking of wheels, the engine can continue its rotation by slippage of the torque converter and hence it is possible to prevent the occurrence of engine stall.
According to the above anti-lock function, in the event the wheels are locked by braking with the brakes, the braking force for the wheels is decreased to prevent locking of the wheels. On the other hand, when braking with the brakes is not performed, that is, when wheels are locked with the force of engine brake, there may be adopted a method wherein the force of engine brake is decreased, i.e., the change gear ratio in the transmission is set to the highest side, to prevent wheel locking.
In this connection, there may be adopted a configuration according to the thirteenth aspect of the present invention, wherein when starting the anti-lock function of the brakes, the brake control unit transmits to the transmission control unit a command as important information to control the change gear ratio of the transmission to make the ratio of input number of revolutions to output number of revolutions in the transmission smaller.
By carrying out the anti-lock function in this way, the occurrence of an accident on a snow-covered road or a frozen road caused by wheel locking is prevented.
Further, in a vehicle equipped with a continuously variable transmission as a component, it is desirable that the change gear ratio be returned to the lowest side until the vehicle stops. Where the change gear ratio cannot be returned to the lowest side until vehicle stop due to sudden braking, it is desirable to make an auxiliary control for increasing the engine torque and thereby restoring the change gear ratio to the low side.
More specifically, it is desirable to adopt a configuration according to the fourteenth aspect of the present invention wherein the important information transmitting means in the transmission control unit transmits to the power control unit information as important information to change gear ratio to make the ratio of input number of revolutions to output number of revolutions in the continuously variable transmission larger. And, when the power control unit receives the important information from the transmission control unit while the vehicular brakes are in operation, the control means provided therein controls to enhance the driving force of the driving force generator.
In this case, if there is adopted, as the driving force generator which the power control unit controls, an internal combustion engine as in the fifteenth aspect of the present invention, as a control by the control means in the power control unit, at least a control is executed such as an intake volume increasing control for increasing the amount of intake air to the engine and an injection volume increasing control for increasing the amount of fuel to be injected to the engine.
A certain type of a vehicle is equipped with a radar system for measuring the distance between the vehicle and an object present ahead of the vehicle for preventing collision of the two. In such a vehicle, whether there is a danger of collision or not is determined based on the distance from the object present ahead of the vehicle thus measured by the radar system and the vehicle speed and a travel control is made for avoiding the collision. Also in this case, it is necessary that the determination on collision and a countermeasure thereto be done as quickly as possible.
In the vehicle being considered, such a requirement can be met by adopting a configuration according to the sixteenth aspect of the present invention, wherein information from the radar system is input to the manager control unit. The second important information transmitting means determines whether the danger of collision between the vehicle and an object present ahead of the vehicle is high or not based on the information provided from the radar system. And, if the result is affirmative, the second important information transmitting means transmits to the corresponding component control unit a deceleration command as important information for causing a predetermined component to decelerate the vehicle.
According to this configuration, in the manager control unit, an operation guide for making a deceleration control best suited for avoiding collision is decided. Or, a manipulated variable therefor is calculated, and it is possible to let each component control unit to execute a desired control quickly.
As concrete methods for the deceleration control, various methods are available, of which a suitable one may be selected in consideration of suppressing shock of the vehicle caused by the urgency of the deceleration control.
If the urgency of the deceleration control is not so high, it is preferable to adopt a configuration according to the seventeenth aspect of the present invention wherein the deceleration control is made by decreasing the vehicular driving force. In this case, the second important information transmitting means may transmit a command for decreasing the driving force which the driving force generator mounted on the vehicle generates, as a deceleration command, to the power control unit which controls the driving force generator. This is preferred because the driving force of the driving force generator decreases gradually by the inertia thereof, allowing the deceleration control to be carried out in a relatively gentle manner. Therefore, the shock which the vehicle undergoes does not become so large.
If the danger of collision cannot be avoided by such a driving force decreasing control, it is proposed to adopt a configuration according to the eighteenth aspect of the present invention wherein the deceleration control is assisted by a brake control using the transmission. According to this configuration, the second important information transmitting means transmits a command for setting the change gear ratio of the transmission mounted on the vehicle in a direction in which the ratio of input number of revolutions to output number of revolutions in the transmission becomes larger, as a deceleration command, to the transmission control unit. By adopting such a control method, engine brake is exerted on the vehicle, thus permitting the vehicle to decelerate quickly.
If it will be impossible to avoid the danger of collision even by the adoption of such a control method, it is proposed to add a braking force induced by the brakes as in the nineteenth aspect of the present invention. In this case, the second important information transmitting means transmits a command for increasing the braking torque generated by the brakes mounted on the vehicle, as a deceleration command, to the brake control unit which controls the brakes.
Adding the braking force induced by the brake system to the deceleration control may produce a large shock of the vehicle, but is regarded as being unavoidable for the prevention of collision.
According to the integrated vehicle control system of the present invention, a plurality of components mounted on a vehicle are controlled integratedly to control the behavior of the entire vehicle induced by operations of the plural components. The control system comprises component control units for controlling the components respectively and a manager control unit which issues an operation guide command to each of the component control units for bringing the behavior of the entire vehicle to a target state. It is not always necessary to implement these control units by independent hardware configurations. For example, a specific component control unit and a manager control unit may be implemented using a single control unit constituted by a microcomputer and the other component control units may be implemented by the operation of a control unit different from the control unit.
However, since the design of each control unit is performed for each hardware configuration, if plural control unit functions are implemented in a single control unit, the design becomes complicated. Moreover, if a specific component is altered due to a design modification for example, there arises the problem that not only the control unit for the altered component but also the other control units incorporated in the single control unit together with the control unit for the altered component are required to be altered.
To solve this problem it is preferable to adopt a configuration according to the twentieth aspect of the present invention wherein the manager control unit and multiple component control units, which constitute the integrated vehicle control system of the invention, are each constituted by an independent electronic unit which is a microcomputer, and are interconnected through a communication line capable of mutually transmitting data.
In this case, if the communication line comprises a communication line for the transmission of important information and a communication line for the transmission of other general information pieces, as in the twenty-first aspect of the present invention, the transmission route is simplified, whereby it is possible to prevent the congestion of communication and to transmit important information more positively and quickly.